The collection of athletes’ sweat during training or competition is a common practice in sports science. Sodium ([Na + ]), potassium ([K + ]), and/or chloride ([Cl − ]) concentrations are measured to estimate athletes’ sweat electrolyte losses to determine electrolyte balance or inform personalized
Lindsay B. Baker, Kelly A. Barnes, Bridget C. Sopeña, Ryan P. Nuccio, Adam J. Reimel and Corey T. Ungaro
Hedy C. Reynolds, Loren Cordain, Mary A. Harris and Sheri Linnell
Thirteen trained runners were studied to determine whether postexercise glucose ingestion contributes to electrocardiogram (ECG) alterations by enhancing decreases in serum potassium (K+) concentrations. For the two randomly ordered trials, subjects ingested a 100 g (25% w/v glucose polymer) drink, either alone or with the addition of 3 g of potassium chloride (KCI), within 15 min following a 90-min run. ECG parameters, serum
Fredric Goss, Robert Robertson, Steve Riechman, Robert Zoeller, Ibrahim Dabayebeh, Niall Moyna, Nicholas Boer, Jennifer Peoples and Kenneth Metz
This investigation evaluated the effect of oral potassium phosphate supplementation on ratings of perceived exertion (RPE) and physiological responses during maximal graded exercise tests (GXT). Eight highly trained endurance runners completed a GXT to anchor the Borg 15-point RPE scale and two double-blind counterbalanced GXTs. Subjects ingested either 4,000 mg · day−1 of phosphate (PHOS) or a placebo (PLA) for 2 days. Two weeks separated GXTs. Phosphate levels obtained immediately prior to the GXTs were greater in PHOS than PLA. No differences between PHOS and PLA were noted for the submaximal and maximal physiological responses. RPE for the overall body were lower during PHOS than PLA at intensities corresponding to 70–80% of V̇O2max. This suggests that oral potassium phosphate supplementation mediates perceived exertion during moderately intense exercise.
Constance B. Christ, Mary H. Slaughter, Rachel J. Stillman, Timothy G. Lohman and Richard A. Boileau
Variability associated with the effects of gender, race, maturation (ML), and age on the potassium content of the fat-free body (K/FFB) was investigated in 163 males and 112 females ages 8 to 30 years. Measures of body density (hydrostatic weighing), bone mineral content (single photon absorptiometry), total body water (modified deuterium dilution), and whole body potassium (40K spectroscopy) were obtained. FFB was calculated using a multicomponent equation which accounted for the variability in FFB mineral and water content. Subjects were classified by maturation as prepubescent, pubescent, postpubescent, and adult (Tanner stages). Least-squares multiple regression analysis revealed significant (p<.05) effects of gender and maturation as well as an interaction between whites and blacks with maturation. The significant increase in K/FFB across maturation and age was most evident in the male sample for both racial groups, with K/FFB increasing from 2.37 in prepubescents to 2.54 in adults. The magnitude of increase in K/FFB across maturation was smaller and not statistically significant within the female sample. Hence, consideration of gender, maturation, and age is important in estimating FFB from total body potassium.
Mark A. Tarnopolsky, Kerry Dyson, Stephanie A. Atkinson, Duncan MacDougall and Cynthia Cupido
We studied the effects of different CHO supplements on exercise metabolism (1 hr at 75%
Donal Murray, Kevin C. Miller and Jeffrey E. Edwards
Although exercise-associated muscle cramps (EAMC) are common in ultradistance runners and athletes in general, their etiology remains unclear. EAMC are painful, sudden, involuntary contractions of skeletal muscle occurring during or after exercise and are recognized by visible bulging or knotting of the whole, or part of, a muscle. Many clinicians believe EAMC occur after an imbalance in electrolyte concentrations, specifically serum sodium concentration ([Na+]s) and serum potassium concentration ([K+]s). Studies that have established a link between EAMC occurrence and serum electrolyte concentrations after an athletic event are unhelpful.
Focused Clinical Question:
Are [Na+]s and [K+]s different in athletes who experience EAMC than noncrampers?
Scott J. Montain, Samuel N. Cheuvront and Henry C. Lukaski
Uncertainty exists regarding the effect of sustained sweating on sweat mineral-element composition.
To determine the effect of multiple hours of exercise-heat stress on sweat mineral concentrations.
Seven heat-acclimated subjects (6 males, 1 female) completed 5 × 60 min of treadmill exercise (1.56 m/s, 2% grade) with 20 min rest between exercise periods in 2 weather conditions (27 °C, 40% relative humidity, 1 m/s and 35 °C, 30%, 1 m/s). Sweat was collected from a sweat-collection pouch attached to the upper back during exercise bouts 1, 3, and 5. Mineral elements were determined by using inductively coupled plasma-emission spectrography.
At 27 °C, sweat sodium (863  µg/mL; mean [SD]), potassium (222  µg/mL), calcium (16 ) µg/mL), magnesium (1265  ng/mL), and copper (80  ng/mL) remained similar to baseline over 7 h of exercise-heat stress, whereas sweat zinc declined 42–45% after the initial hour of exercise-heat stress (Ex1 = 655 , Ex3 = 382 , Ex5 = 355  µg/mL, P < 0.05). Similar outcomes were observed for sweat zinc at 35 °C when sweat rates were higher. Sweat rate had no effect on sweat trace-element composition.
Sweat sodium, potassium, and calcium losses during multiple hours of sustained sweating can be predicted from initial sweat composition. Estimates of sweat zinc losses, however, will be overestimated if sweat zinc conservation is not accounted for in sweat zinc-loss estimates.
Michael F. Bergeron, Carl M. Maresh, Lawrence E. Armstrong, Joseph F. Signorile, John W. Castellani, Robert W. Kenefick, Kent E. LaGasse and Deborah A. Riebe
Twenty (12 male and 8 female) tennis players from two Division I university tennis teams performed three days of round-robin tournament play (i.e., two singles tennis matches followed by one doubles match per day) in a hot environment (32.2 ±
Michael F. Bergeron
A 17-year-old, nationally ranked, male tennis player (AH) had been experiencing heat cramps during tennis match play. His medical history and previous physical exams were unremarkable, and his in-office blood chemistry profiles were normal. On-court evaluation and an analysis of a 3-day dietary record revealed that AH's sweat rate was extensive (2.5 L · hr−1) and that his potential daily on-court sweat sodium losses (89.8 mmol · hr of play') could readily exceed his average daily intake of sodium (87.0-174.0 mmol · day−1). The combined effects of excessive and repeated fluid and sodium losses likely predisposed AH to heat cramps during play. AH was ultimately able to eliminate heat cramps during competition and training by increasing his daily dietary intake of sodium.
Jay L. Tuttle, Jeffrey A. Potteiger, Blanche W. Evans and John C. Ozmun
This study examined the effects of aspartate supplementation (ASP) on plasma ammonia concentrations ([